This invention relates to power shovels and more particularly to a crowd drive assembly for a power shovel having a main frame, a boom connected at a lower end thereof to the main frame, a dipper handle connected to the boom and a dipper pivotally connected to the dipper handle, as well as the crowd drive assembly which operates to extend and retract the dipper handle relative to the boom during the shovel's cycles of operation and the structure for guiding and supporting the dipper handle.
Conventional types of power shovels generally utilize a crawler assembly, a main frame rotatably mounted on the crawler assembly, a boom connected at its lower end to the main frame, a gantry mounted on the main frame, and pendants interconnecting the boom with the gantry for maintaining the boom at a predetermined angle. A dipper handle is mounted on the boom for longitudinally reciprocal and pivotal movement, a dipper is connected to the end of the dipper handle, a hoist line is connected to the dipper and passes around a sheave mounted at the point of the boom and which is operatively connected to a hoist mechanism mounted on the main frame. A crowd drive mechanism is provided whereby the dipper handle is extended or "crowded" for digging and retracted.
Earlier forms of power shovels utilized a dipper handle which was a single member, and the dipper handle was driven for crowding by a rack and pinion arrangement, e.g., a rack mounted on the dipper handle and a pinion driven on a shipper shaft journaled through the boom. Customarily, the single member dipper handle was supported and guided by a yoke member which received the dipper handle and which has pivotally mounted directly on the shipper shaft.
As machines grew larger, the increased loads being experienced by the dipper handle, yoke block and boom and the mechanisms by which these could be handled caused a change in the design of the dipper handle. These loads were especially troublesome when the corners of the dipper receive the principal loading, as in corner digging, and when a side loading of the dipper occurs, as when the dipper is being used to load a truck. These forces essentially create motions of the dipper handle about two axes in the vertical plane of the dipper handle. Firstly, there is a torsional motion of the dipper handle about its axis or in substantially a horizontal axis in the aforementioned vertical plane and secondly a side-to-side motion of the dipper handle which can be considered as essentially occurring in a vertical axis in the vertical plane of the dipper handle. The single member dipper handle was generally replaced in most larger machines by a bifurcated dipper handle with the ends of the handle extending around the outside of the boom. A saddle block or yoke member carries the bifurcated dipper handle, and this form of yoke member is, as well, mounted directly on the shipper shaft. Thus, in both forms of machines as now conventionally built, the loads received by the yoke member from the dipper handle are transferred to the shipper shaft prior to being transmitted to any other part of the structure. This can result in bending or otherwise distorting the shipper shaft requiring replacement, or in the alternative, the manufacture of an unusually sturdy, and therefore undesirably heavy, shipper shaft.
Accordingly, it is an object of this invention to provide an improved crowd drive assembly for a power shovel of the type described hereinabove.
Another object of this invention is to provide an improved structural arrangement for a crowd drive mechanism in a power shovel of the foregoing type wherein loads experienced by the dipper handle are transferred directly to the boom.
A further object of this invention is to provide an improved crowd drive assembly and dipper handle supporting structure wherein a single member dipper handle can be used.
An additional object of this invention is to provide an improved crowd drive assembly for a power shovel of the foregoing type wherein the structural member carrying the dipper handle in the boom without intervention of other structural members such as a shaft is mounted directly on the boom whereby loads experienced by the dipper handle are transferred directly thereto.
Still another object of this invention is to provide an improved dipper handle supporting structure in a crowd drive assembly in a power shovel of the type described hereinabove wherein either the yoke member or the shipper shaft and parts mounted thereon can be readily removed for servicing without requiring that the entire structure be disassembled.